English,c.1840, unsigned, constructed of finely turned and polished Lignum Vitae, the central rotating specimen holder with corresponding engraved labels, Nitre, Borax, blank, Quartz, Topaz, Calc Spar, each viewed between a linear Tourmaline polariser, height 14cm. [CITES]

Note: This lot contains or is made of ivory and cannot be imported into the USA or any country within the EU.

Footnote: this elegant little viewer demonstrates conoscopic interference patterns or interference figures which are a pattern of birefringent colours crossed by dark bands (or isogyres) of the mineral being viewed.